Emergency exam help - calculating interest

Hey guys, yeah this is another homework help request, but I'm really at a loss here. I'm supposed to write a script that will calculate balances after interest rates and output them over a 12 month period.

I'm at a brick wall. The script I have compiles just fine, but when executed with the test file I get an error that the value for saver1 and saver2 is an incompatible type. I can't find what I'm missing here. Can anybody point me in the right direction?